1. Field of Disclosure
The present disclosure relates generally to the field of combustion furnaces and methods of use, and more specifically to improved submerged combustion melters and methods of use in producing molten glass from recycled glass mat and other rolled glass materials, such as wound rovings of continuous glass filament.
2. Related Art
Glass mat products such as fiber glass and mat and insulation mat are characterized by a nonwoven mat of glass fibers held together with a binder. Recycling or reclamation of glass mat products has been disclosed in and practiced previously. Many of these disclosed methods involve crushing the glass mat to a maximum fiber or particle size prior to re-melting. Other processes involve a heating step prior to grinding whereby the binder is first burned off without melting the glass fibers. In older processes the binders were typically desired to be removed prior to re-melting because the remnants of the binders may cause production of unsatisfactory glass products.
Submerged combustion has been proposed in several patents for application in commercial glass melting, including U.S. Pat. Nos. 4,539,034; 3,170,781; 3,237,929; 3,260,587; 3,606,825; 3,627,504; 3,738,792; 3,764,287; 6,460,376; 6,739,152; 6,857,999; 6,883,349; 7,273,583; 7,428,827; 7,448,231; 7,565,819, and 7,624,595; published U.S. Pat. Application numbers 2004/0168474; 2004/0224833; 2007/0212546; 2006/0000239; 2002/0162358; 2009/0042709; 2008/0256981; 2007/0122332; 2004/0168474; 2004/0224833; 2007/0212546; and 2010/0064732; and published PCT patent application WO/2009/091558, all of which are incorporated herein by reference in their entireties. In submerged combustion glass melting, the combustion gases are injected beneath the surface of the molten glass and rise upward through the melt. The glass is heated at a higher efficiency via the intimate contact with the combustion gases. However, submerged combustion burners have not heretofore been used to recycle or reclamate glass mat products without first crushing the mat products to reduce the size of the glass fibers. Materials melted with submerged combustion burners may include at least silica-bearing material (such as sand), alkaline earth metal oxide-bearing material (such as limestone or dolomite), boron-oxide-bearing material (such as borax), sodium oxide raw material (such as sodium carbonate), alumina raw material (such as feldspar), and/or cullet.
U.S. Pat. No. 4,397,692 discloses methods and apparatus for the reclamation of inorganic fibers from waste continuous strips of inorganic fibers. The '692 patent mentions another, previous recapture technique is to feed the recaptured fibers directly into the melting furnace with virgin glass batch. The difficulty with this approach, according to the '692 patentees, is that a major amount of the cost of the fiber is not in the material but, in the cost of production and, by melting the fibers, that amount is lost. In addition, the cost of processing the fibers for feeding to a batch furnace is equal to or greater than the cost of the batch it replaces, making this process economically unattractive. According to the Abstract of the '692 patent, a binding agent, such as an organic binder, must be removed before the fibers can be reused or further processed. One or more layers of continuous strips are conveyed to a heating zone where the strips are supported along a predetermined path as a heating fluid is drawn rapidly through the strips to decompose the binder. Unfortunately, the '692 patent suggests that in the case where binder is still present on the fibers in unacceptable levels, these non-reclaimable fibers may be dumped for subsequent disposal. This practice is now unacceptable, due to the lack of landfill space available, and due to the justifiably increased concern for the environment. The '692 patent does not disclose, teach or suggest roll-feeding of fiber glass mat scrap or rovings, or folding shoes, or nip rollers being used to feed fiberglass mat scrap to a melter.
U.S. Pat. No. 4,422,862 describes a process for feeding scrap glass to a glass melting furnace. The scrap glass is fed onto a blanket of batch in the furnace so that organics are burned off before the scrap melts. The scrap glass is either first hammermilled or crushed before it is fed to the glass melting furnace, or enters the furnace in the form of fluffy, fine textured scrap that floats on the batch blanket. There is no teaching or suggestion of roll-feeding, or folding shoes, or of nip rollers being used to feed the scrap to the melter. There is disclosed use of a conveyor belt, but the patentee states “In FIG. 2, scrap glass is manually fed onto belt conveyor 12 at a controlled rate. The cullet glass previously has been processed through a crusher (not shown).” Clearly, crushing is involved, as the patentee states “the crushing advantages are fluffy fine textured scrap that floats on the batch cover allowing good penetration and binder burn-off by furnace gases.”
U.S. Pat. No. 4,432,780 discloses a method of reclaiming chemically coated glass scrap. The scrap is introduced into the oxidizing atmosphere of a hydrocarbon-fuel fired glass melting furnace. Some of the glass is melted with the unmelted portion being melted with the glass batch as it moves through the furnace. The patentees state that “The scrap glass can be introduced into the furnace in any suitable form. Preferably, it will be introduced in particulate form up to about 1¼ inch screen size by means of a blowing wool machine, one or more machines being used depending upon the quantity of scrap glass being introduced.” Despite the broad introductory statement that “the scrap glass can be introduced in any suitable form”, the particulate form is the only form that is disclosed. Thus, this patent fails to disclose, teach, or suggest roll-feeding, or folding shoes, or of nip rollers being used to feed scrap to the melter.
U.S. Pat. No. 4,309,204 discloses a process and apparatus for remelting scrap glass fibers. The removal of binder and remelting of the scrap are carried out in one operation, and the resulting molten scrap fibers are fed directly into a conventional glass melting furnace. Granular raw glass batch also is fed into the glass melting furnace. FIGS. 1 and 2 of the '204 patent show a glass feeder feeding glass strands to a melter through rotating shaft feeders. Thus, this patent fails to disclose, teach, or suggest roll-feeding of fiber glass mat scrap or rovings, or folding shoes, or nip rollers being used to feed fiberglass mat scrap to a melter.
JP 2000351633 is another example method and apparatus for recycling fiber glass waste. The reference discloses use of a burner to feed waste glass fiber to a glass melting tank furnace. The recycling apparatus is provided with a hopper for storing waste glass fiber cut to proper size and a constant-rate discharging apparatus to discharge the waste material at a constant rate. This reference fails to disclose, teach, or suggest roll-feeding of fiber glass mat scrap or rovings, or folding shoes, or nip rollers being used to feed fiberglass mat scrap to a melter.
JP 2002120224 discloses a method for recycling glass fiber-reinforced thermoplastic resin characterized by feeding the glass fiber-reinforced thermoplastic resin for recycling to a vessel wherein a non-recycled thermoplastic resin is under melted condition. Thus, the approach here is not to feed the fiber glass reinforced waste into a glass tank furnace, but into a tank of molten thermoplastic resin. This reference therefore fails to disclose, teach, or suggest roll-feeding of fiber glass mat scrap or rovings, or folding shoes, or nip rollers being used to feed fiberglass mat scrap to a glass tank melter.
It would be an advance in glass mat recycling to develop methods and apparatus for recycling and/or reclaiming glass mat and similar items, such as wound roving of continuous glass filament, that avoid the significant processing needed to shred such materials and/or mill it into a fine powder for re-melting, while taking advantage of the efficiency of submerged combustion burners, to increase melter throughput and produce high quality molten glass.